Fix the bug that buildah reads /var/run/containers.. as authentication file.(in readme files it should be /run/containers/uid).
Add `buildah login`, `buildah logout` to close#1329, enable to use buildah login before running buildah bud for multi-stage bud and avoiding using --creds flag.
Signed-off-by: Qi Wang <qiwan@redhat.com>
Closes: #1501
Approved by: rhatdan
Qi Wang